Prescription ·Strong evidence ·Reviewed May 2026
A macrolide antibiotic with activity against gram-positive cocci, atypical organisms (Mycoplasma, Chlamydia, Legionella), and Mycobacterium avium complex (MAC). Used for community-acquired pneumonia, acute bacterial sinusitis, pharyngitis, acute exacerbations of chronic bronchitis, skin infections, and as a key component of H. pylori triple therapy. Notable for significant CYP3A4 inhibition, which causes numerous drug interactions.
The bottom line
Evidence rating strong. Most-documented uses: treats community-acquired pneumonia, key component of h. pylori triple/quadruple therapy, treats mac infections in immunocompromised patients. 10 sources indexed (1991–2025), with 5 interaction records on file.
Core mechanism
Binds to the 50S ribosomal subunit at the 23S rRNA peptidyl transferase center, blocking peptide chain elongation and inhibiting bacterial protein synthesis. Primarily bacteriostatic. Its active metabolite, 14-hydroxyclarithromycin, also has antibacterial activity and acts synergistically with the parent compound against H. influenzae. Clarithromycin is a potent inhibitor of CYP3A4, CYP2C9, and P-glycoprotein, leading to significant drug-drug interactions.
Bioavailability approximately 50%. Food improves tolerability. Extended-release tablets (Biaxin XL) should be taken with food to optimize absorption. IMPORTANT: Potent CYP3A4 inhibitor, numerous significant drug interactions.5
Nutrients this medication can lower over time, and what to replace.
Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients.
Clarithromycin is a potent CYP3A4 inhibitor that dramatically increases simvastatin plasma levels (up to 10-fold), greatly increasing the risk of severe rhabdomyolysis, a potentially fatal muscle breakdown condition.
Recommendation: Contraindicated. Suspend simvastatin during clarithromycin treatment. If statin therapy is needed, use pravastatin or rosuvastatin (not CYP3A4 metabolized).
Clarithromycin inhibits CYP3A4, increasing atorvastatin levels. While less dramatic than simvastatin interaction (atorvastatin is partially CYP3A4 metabolized), the risk of myopathy and rhabdomyolysis is still significantly elevated.
Recommendation: Limit atorvastatin to 20 mg daily when used with clarithromycin. Consider azithromycin as alternative macrolide (no CYP3A4 inhibition) or pravastatin/rosuvastatin as alternative statin.
St. John's Wort is a potent inducer of CYP3A4, the primary enzyme that metabolizes clarithromycin. Co-administration substantially lowers clarithromycin serum levels and can result in treatment failure. The induction effect persists for days to weeks after stopping St. John's Wort.
Recommendation: Avoid St. John's Wort during clarithromycin therapy and for at least 2 weeks before starting. Use an alternative antibiotic or alternative antidepressant strategy if both are needed.
Probiotic supplementation during clarithromycin therapy, including during H. pylori triple therapy, reduces antibiotic-associated diarrhea and improves tolerability. Several meta-analyses show probiotics also improve H. pylori eradication rates when added to standard therapy.
Recommendation: Take probiotics throughout your clarithromycin course, separated by at least 2 hours from each antibiotic dose. Continue for at least 1 week after the antibiotic ends.
Saccharomyces boulardii reduces antibiotic-associated diarrhea during clarithromycin therapy and is unaffected by the antibiotic because it is a yeast. It also has supportive evidence for improving H. pylori eradication when added to standard triple therapy.
Recommendation: Take Saccharomyces boulardii throughout your clarithromycin course. Timing flexibility is greater than with bacterial probiotics. Continue for at least 1 week after the antibiotic ends.
Numbered references. Citations throughout the page link here.
Dossouvi KM, Bouyo T, Sognonnou S et al.. Clarithromycin-resistant Helicobacter pylori in Africa: a systematic review and meta-analysis. Antimicrobial resistance and infection control. 2025
Sholeh M, Khoshnood S, Azimi T et al.. The prevalence of clarithromycin-resistant Helicobacter pylori isolates: a systematic review and meta-analysis. PeerJ. 2023
Bashir NZ, Sharma P. Clarithromycin as an adjunct to periodontal therapy: a systematic review and meta-analysis. International journal of dental hygiene. 2022
Huang Z, Zhou B. Clarithromycin for the treatment of adult chronic rhinosinusitis: a systematic review and meta-analysis. International forum of allergy & rhinology. 2019
Harb AH, Chalhoub JM, Abou Mrad R et al.. Systematic review and meta-analysis: full- vs. half-dose anti-microbials in clarithromycin-based regimens for Helicobacter pylori eradication. Alimentary pharmacology & therapeutics. 2015
Wood MJ. The tolerance and toxicity of clarithromycin. The Journal of hospital infection. 1991
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